The present invention relates to an imaging system.
Machine vision systems are commonly used in industry for high speed inspection. In particular, these systems are used to obtain digital images of objects in order to determine, with a computer, whether the object is of xe2x80x9cacceptablexe2x80x9d quality with respect to predetermined specifications.
An example of an application for a machine vision system is inspection of semiconductor chips and semiconductor device packages, both leaded and grid array. In such a system, for leaded packages, automatic inspection using machine vision is carried out, in particular, with respect to defective leads and defects on leads. In a typical system, a number of device packages are imaged while in their carrier tray, and a computer compares the images to device package specifications stored at an earlier time. Many of these systems are fairly good at detecting metallic, highly reflective defects such as slivers or burrs found on leads. However, these conventional systems have difficulty detecting foreign, non-metallic matter, such as fibers and other contamination.
Backlight techniques can be used for leaded packages, but they require handling of each and every device which is potentially damaging to the fragile leads. Backlighting cannot be used on chips or grid array packages.
According to an example embodiment of the present invention, a system is provided for imaging an object. The system includes a light source for illuminating the object with light, the light from the light source having a first wavelength. The system further includes an image capturing device and a filter device. The filter device is transmissive for light having a wavelength which is different than the first wavelength, and reflective for light at the first wavelength, the image capturing device capturing an image of at least a portion of the object using light transmitted through the filter device. The system may further include a dark field illumination system.